Bearing deviation indicator

ABSTRACT

The disclosure describes an improved bearing deviation indicator for detecting and tracking noise sources such as, for example, those produced by vehicles. The device comprises a rotatable acoustic array which generates electrical analogs of the noise waves which are coupled to novel signal processing means which produce signals indicative of alignment of the acoustic array with the noise source or deviation of the acoustic array from the noise source. The signals are coupled to servo means which in response thereto rotates the array to align it with the noise source.

Uited States Patent 1 [111 3,763,465

Tatgc et a1. Oct. 2, 1973 1 BEARING DEVIATION INDICATOR PrimaryExaminerRichard A. Farley Attorney-Harry M. Saragovitz, Edward J. Kellyand [75 Inventors: Robert B. Tatge; Richard J. Wells, both ofSchenectady, NY. Herbert [73] Assignee: The United States of America as[57] ABSTRACT represented b th Secretary The disclosure describes animproved bearing deviaf h A tion indicator for detecting and trackingnoise sources such as, for exam le, those roduced by vehicles. The [22]Flled: 1971 device comprises rotatable acoustic array which gen- [21] AN 122511 erates electrical analogs of the noise waves which are coupledto novel signal processing means which prol52] [1.8. CI. 340/16 R,340/6R,343/100 CL duce signals indicative of alignment of the acoustic [51Int. Cl. Gls 3/80 array with the noise source or deviation of theacoustic [58] Field of Search 343/100 CL; 340/6 R, array from the noisesource. The signals are coupled to 340/6 S, 16 R servo means which inresponse thereto rotates the array to align it with the noise source.

[56] References cued Claims, 3 Drawing Figures UNITED STATES PATENTS3,154,778 /1964 Kock 343/100 CL 3,348,195 10/1967 Spandock 340/16 R )1L-au l3 /4 J4 J4 v Lorre/afar 46 4/ 48 50 carve/afar -52 44 i 4 F 42 4;iflervo o BEARING DEVIATION INDICATOR l-leretofore bearing deviationindicators employed for locating a noise source have not had thecapability of generating an error signal which is very sensitive toangular error. These indicators employed crossed directive acousticarrays, each formed by a multiplicity of microphones. The error signalis produced by mounting the arrays at an angle with one another, thuseffectively crossing their reception beams. The outputs of these arraysare processed by electronic means ineluding amplifiers in such a mannerthat when the outputs of the processing means are 180 out-of-phase wheneach array sees acoustic signals of the same phase. However, suchbearing deviation indicators which are dependent upon amplifiers do notproduce a great rate of change of error signal per degree of angledeviation from the target or noise source.

Accordingly a prime object of the invention is an improved bearingdeviation indicator wherein a great rate of change of error signal perdegree of angle deviation from the target or noise source is obtained.

The novel features that are considered characteristic of the inventionare set forth with particularity in the appended claims. The inventionitself, however, both as to its organization and method of operation aswell as additional objects and advantages thereof will be understoodwhen read in conjunction with the accompanying drawing in which:

FIG. 1 is a schematic representation of the invention;

FIG. 2 is a block diagram of a correlator; and

FIG. 3 is a graph illustrating the great rate of change of error signalper degree of angle deviation from the target.

Referring now to FIG. 1, reference numeral indicates the improvedbearing deviation indicator which is designed to be used after target,noise source, has been acquired and roughly trained thereon by othermeans such as a conventional bearing deviation indicator means 12 whichdoes not generate an error signal very sensitive to angular error. Inone embodiment of the bearing deviation indicator 12, two directiveacoustic arrays 13 and 14 are employed, each consisting of eightlongitudinally spaced connected microphones 15 and 16, respectively. Theerror signal is produced by mounting the arrays 13 and 14 at an angle toeach other with an equal number of microphones being disposed on eachside of each array at the point of intersection of the arrays, thuseffectively crossing their receiving beams. The output of array 14 iscoupled to the input of an electronic amplifier 17 as indicated by 18and the output of array 13 is coupled to electronic amplifier 19 asindicated by 20. The outputs of amplifiers 17 and 19 are connected totransformers 20 and 21 to rectifying diodes 22 and 23 which have theiroutputs bridged by summing means comprising series connected resistors24 and 25. The summing point 26 is coupled to an integrating capacitor27 which in turn is connected by conductor means 28 through switch means29 to servo means 30 which is coupled to a vertical mast 31 for thepurpose of rotating array 12 which is mounted thereon. An AGC circuitcoupled to the outputs of amplifiers l7 and 19 and consisting of seriesconnected diode rectifier 32 and parallel resistor capacitor 33 providesmeans whereby the sum of the outputs of said amplifiers, amplifiedsignals, is rectified and applied as an AGC to the amplifiers so thatthe sum signal is held constant in level. The crossed arrays 13 and 14outputs are amplified by amplifiers l7 and 19, respectively, thenrectified by rectifiers 22 and 23 such that the outputs of therectifiers are out-of-phase when each array sees signals of the samephase. When the crossed array is trained in response to the integratedoutput in view of the deviation of the array from the noise source 32through servo means 30 to a point where its axis points directly tonoise source 32, the rectified signals exactly balance out giving a netoutput of zero. When the crossed array deviates or is deviated fromnoise source 32, the sum of the rectified signals will swing positive ornegative depending on the direction of the error, that is, the degreethat the crossed array is pointed away from either side of the noisesource. Of course it is to be understood that the foregoing describesbut one means which may be employed for acquiring the noise target androughly training the array 10 utilized in the invention.

The improved bearing deviation indicator 10 uses polarity-coincidencecorrelators in combination with an acoustic array, subsequentlydescribed, to achieve bearing error information and means responsivethereto whereby the array tracks and pinpoints the noise source. In apreferred embodiment the acoustic array employed in the inventioncomprises two crossed microphone arrays 34 and 35 having the same numberof microphones as the arrays of conventional bearing deviation indicator12, but now each array is connected as two multi-element microphonearrays 34 and 34", and 35' and 35", each shaded for optimum side-lobesuppression, that is, the microphones of each array are connected in amanner so as to form a narrow receptive beam wherein the sensitivity ofadjacent microphones decreases from the center of the array to theextremity thereof. Crossed arrays 34 and 35 are mounted at theirintersection on the shaft 31 below the crossed arrays 13 and 14 inacoustical alignment therewith. Each array thus arranged is directiveand discriminates against noise sources outside of the acceptance angleof the complete array. The outputs of arrays 35' and 35 of array 35 arecoupled to a first input 36 and a second input 37 of a correlator 38 asindicated by 39 and 40, respectively, whereby the A.C. outputs of themicrophones of these arrays generated in response to the noise sourceare applied to inputs 36 and 37 and processed by a polarity-coincidencecorrelator 38 to produce a positive going signal at the output 40'thereof. The output of array 34' of array 34 is coupled as indicated by44 through a 180 phase reversal means 45 to a second input 42 of apolarity-coincidence correlator 43 and the output of array 34" thereofas indicated by 46 is directly coupled to a first input 41 of correlator43 whereby the A.C. outputs of the microphones of these arrays generatedin response to the noise source are applied out of phase to the inputsof correlator 43 which processes these out of phase inputs to produce anegative going signal at its output. Thus it can be seen that an errorsignal is generated since the output of correlator 38 is arranged to bea plus value for perfect correlation while the output of correlator 43is made to be a minus value and that the sum of the correlator outputswill swing positive or negative as the crossed acoustic arrays swingfrom one side of the noise source to the other. The sum of the outputsof correlators 38 and 43 is obtained by summing means consisting ofseries connected resistors 49 and 50 bridged between the outputs ofpolarity-coincidence correlators 38 and 43 with the intermediatejunction 51 being the summing point which is coupled by conductor means52 through switch means 29 to servo means 30 which in response to thesummed error signals of the polarity-coincidence correlators 38 and 43rotates shaft 31 whereby the center of the crossed acoustic arraycomprising longitudinally disposed microphone arrays 34 and 35 isbrought into alignment with the noise source 32.

The polarity-coincidence correlators 38 and 39 may each consist of thearrangement shown in the block diagram of FIG. 2. Infinite clipper 53,for example, has coupled to its input 36 the output signals ofmicrophone array 35 and infinite clipper 54 has coupled to its input 37the output signal of microphone array 35 whereby each input signal isinfinitely and symmetrically clipped, reducing each signal to arectangular wave having the same zero crossings as the original signals.These two clipped signals are then added by means of adder 55 coupledthereto, the output of which is full-wave rectified by full-waverectifier 56 and the result integrated by integrator 57 which provides apos itive going output signal to which servo means 30 responds.Similarly, the output signals of microphone arrays 34' and 34" areprocessed by identical correlator 43 with the exception that a phasereversal means is coupled between one of the said array outputs and aninput of the correlator resulting in a negative going error signal beingobtained at the output 48 of correlator 43.

In FIG. 3 the solid curve represents the calculated error signal for aconventional bearing deviation indicator, described in conjunction withFIG. 1, and as can be ascertained from examination thereof the rate ofchange of error signal per degree of deviation is very small. From thedash curve representing the calculated error signal of the invention itcan be seen that once the inventive device acquires the target, the rateof change of error signal per degree of deviation is very great thus theinventive device results in quickly and accurately pinpointing thetarget or noise source.

We claim:

1. A bearing deviation indicator for tracking and pinpointing a noisesource and having a great rate of change of error signal per degree ofangle deviation from the noise source comprising in combination:

first and second longitudinally disposed electroacoustical directivearrays crossed at their centers whereby their effective receptive pathsare crossed; said first directive array comprising a first group ofconnected spaced microphones extending outwardly of the center of thearray and a second group of connected spaced microphones extendingoutwardly of the center of the array diametrically opposite to saidfirst group of microphones;

said second directive array comprising a third group of connected spacedmicrophones extending outwardly of the center of the array and a fourthgroup of connected spaced microphones extending outwardly of the centerof the array diametrically opposite to said third group of microphones;

first polarity-coincidence correlator having one input coupled to saidfirst group of microphones and another input coupled to said secondgroup of microphones for processing the electrical analog signalsproduced by said first and second groups of microphones in response tosaid noise source with respect to deviation of said first array fromsaid noise source whereby a positive going signal is produced in theoutput thereof;

a second polarity-coincidence correlator having one input coupled tosaid third group of microphones and another input coupled to said fourthgroup of microphones through phase shift means for processing theelectrical analog signals produced by said third and fourth groups ofmicrophones in response to said noise source with respect to thedeviation of said second array from said noise source whereby a negativegoing signal is produced in the output thereof;

summing means bridged acrossed the outputs of said first and secondpolarity-coincidence correlators producing error signals in response tosaid output signals; and

means responsive to said error signals coupled to said directive arrayswhereby said directive arrays are subsequently aligned with the noisesource.

2. The invention in accordance with claim 1 wherein the microphones ofeach said array are shaped for optimum side-lobe suppression.

3. The invention in accordance with claim 2 wherein said summing meanscomprises first and second series connected resistors forming a summingpoint at their junctiOn and bridged across the outputs of said first andsecond polarity-coincidence correlators.

4. The invention in accordance with claim 3 wherein said phase shiftmeans comprises a phase shift means.

5. The invention in accordance with claim 4 wherein said meansresponsive to said error signals comprises servo means adapted to orientsaid directive arrays in response to the error signals.

1. A bearing deviation indicator for tracking and pinpointing a noisesource and having a great rate of change of error signal per degree ofangle deviation from the noise source comprising in combination: firstand second longitudinally disposed electro-acoustical directive arrayscrossed at their centers whereby their effective receptive paths arecrossed; said first directive array comprising a first group ofconnected spaced microphones extending outwardly of the center of thearray and a second group of connected spaced microphones extendingoutwardly of the center of the array diametrically opposite to saidfirst group of microphones; said second directive array comprising athird group of connected spaced microphones extending outwardly of thecenter of the array and a fourth group of connected spaced microphonesextending outwardly of the center of the array diametrically opposite tosaid third group of microphones; a first polarity-coincidence correlatorhaving one input coupled to said first group of microphones and anotherinput coupled to said second group of microphones for processing theelectrical analog signals produced by said first and second groups ofmicrophones in response to said noise source with respect to deviationof said first array from said noise source whereby a positive goingsignal is produced in the output thereof; a second polarity-coincidencecorrelator having one input coupled to said third group of microphonesand another input coupled to said fourth group of microphones throughphase shift means for processing the electrical analog signals produceDby said third and fourth groups of microphones in response to said noisesource with respect to the deviation of said second array from saidnoise source whereby a negative going signal is produced in the outputthereof; summing means bridged acrossed the outputs of said first andsecond polarity-coincidence correlators producing error signals inresponse to said output signals; and means responsive to said errorsignals coupled to said directive arrays whereby said directive arraysare subsequently aligned with the noise source.
 2. The invention inaccordance with claim 1 wherein the microphones of each said array areshaped for optimum side-lobe suppression.
 3. The invention in accordancewith claim 2 wherein said summing means comprises first and secondseries connected resistors forming a summing point at their juncti0n andbridged across the outputs of said first and second polarity-coincidencecorrelators.
 4. The invention in accordance with claim 3 wherein saidphase shift means comprises a 180* phase shift means.
 5. The inventionin accordance with claim 4 wherein said means responsive to said errorsignals comprises servo means adapted to orient said directive arrays inresponse to the error signals.